Electron-beam gun



/NVENTR CHARLES R. KELLY Alforney 3,388,179 ELECTRON-BEAM GUN Charles R. Kelly, Pittsburgh, Pa., assignor to United States Steel Corporation, a corporation of Delaware Filed Oct. 5, 1965, Ser. No. 493,154 3 Claims. (Cl, 313-279) ABSTRACT F THE DISCLOSURE An electron-beam gun including a thermionic emitter is provided 'with a trough-shaped bathe confining electron emission to a limited arc outwardly from the emitter. The bafe is of hour--glass shape longitudinally, i.e., has its mid-portion drawn. in to a width less than that of the end portionsc This tends to correct non-uniform emission along the length of the emitter by reducing emission in the region where it would be greatest, without the use of the invention,

This invention relates to electron-beam guns and, in. particular, to an elongated g-un having provision for achieving a more uniform bombardment of the mass to be heated, along the length of the gun, than has been obtainable hereto-fore,

Electron-beam guns are now extensively used, prin-l cipally for heating material in vacuum processes. In fact, industrial operations .now contemplated require the heatn ing of material. over a width. of several. feet, i.e. metal strip or the surface of a mass of molten metal to be vaporized This necessitates elongated guns and, indeed, the end-to-end assembly of a plurality of guns. An elongated gun 'with a straight tungsten wire as the thermionic electron emitter has the shortcoming that the density of elecrons emitted increases from both ends toward the center because of the cooling effect of the support means and current-supply connections As a result, the density of the electron-beam. delivered and the heating effect thereof, vary considerably across the width of the ma terial or mass to be heated It is therefore the object of my invention to provide an. electron-beam gun capable of delivering a beam of electrons which produces a heating effect with less variation longitudinally of the emittere In a preferred practice of my invention, I provide a trough-shaped backing electrode or shield for the hotwire emitter, which has a pinched-in or necked-down central portiono This portion tends to restrict. the escape of electrons from the midportion of the emitter and causes the build-up of a cloud or' electrons forming a space charge which itself reduces the discharge of electrons from the mid-portion of the emittern The overall res-ult is that there is less difference between the heating edect on the work; (metal strip or evaporand) between the middle and ends of the gun than has been encoune tered using guns available heretoforeu A complete understanding of the 'invention may be obtained from the following detailed description and er;J

plantation which refer to the accompanying drawings il.u l

3,388,279 Patented .lune 11, 1958 side walls lll. The ends are open so the guns may be assembled end-to-end in multiple-unit relation. The elongate character of the gun is apparent from FIGURE l., The base and side walls are at ground potential as is also a sheet-metal accelerating anode 12 carried on the side walls and extending therebetween. Anode 12 has an openN ing or window 13 therein.

A high-voltage (negative) platform 14 is mounted on insulators 15 upstanding on base 10. Insulators 16 are mounted in pairs on platform 14 adjacent the ends thereof. Cross bars 17 of conducting metal join the insulators of each pair. Terminal clips 18 are secured, in alined the electron emitter, extends between them Current-2,

supply conductors (not shown) are connected to the bars 17 and extend to a source of emitter-heating current.

Angle brackets 20 secured to platform 14 support a trough-shaped open-ended backing electrode or shield 21 partially enclosing emitter 19., The side walls of the shield are pinched. in or necked-down at the lmid-portion as indicated at 22. The effect of this shape is to restrict somewhat the outflow of electrons from the emitter at its midportion, compared with the outow adjacent the ends thereof. As shown FIGURE 1, the shape of opening 13 approximates that of shield 21, being slightly larger than the latter overall As previously pointed out` the necked-in mid-portion 22 of shield 21 narrows the exit for electrons passing from. emitter 19 to the anode (mass to be heated), not shownz Thus the resultant heating effect of the electron beam is applied to an area on the mass to be heated opposite the middle of the gun, narrower than the areas opposite the ends of the emittera This tends to smooth out the difference otherwise existing between the heating effect of the beam at various points along the length of the region of impingenceD Although. I have disclosed herein the preferred embodif .ment of my invention, I tend to cover as well any change or modification therein which may be made without den parting from the spirit and scope of the invention as set forth in the claimsa I. elairnz 1, An. electron-beam gun comprising a support, t/ern minals mounted thereon in spaced, relation, an electron emitter wire extending between terminals, and. a trough; shaped backing electrode mounted on the support between it and the wire, the sides of said electrode being pinched :in toward each. other adjacent the mid-portion of the wirec 2e An apparatus as defined in claim 1, characterized by an accelerating anode sheet overlying said backing electrode and having an opening therein conforming in shape to that of said electrode in plann Sie An apparatus as defined in claim 1, characterized by said support being a platform, a base having insulators thereon carying said platform, side walls extending upn Wardly from said base, and an accelerating anode sheet extending between said side. walls,

References Cited UNITED STATES PATENTS 2,532,956 12./ 1950 Simpson. ,w 313-278 X 3,286,117 1,1/1966'- Donlevy e -e 313-279 3,300,676 1/1967 Sterzl l 313-278 JOHN HUCKERT, Primary Examiner.,

R.o F, POLISSACK, Assistant Examiner, 

